The present invention relates to improvements in roller presses, and more particularly to an improved roller construction and method of making the roller which provides surface armoring particularly for high pressure roller presses for pressure comminution of granular material operating as interparticle crushing presses.
In roller presses and crushers, brittle grinding stock is drawn into the nip and is subjected to pressure comminution. What is referred to as interparticle crushing in the nip of a high pressure roller press is also known as product bed comminution wherein the individual particles of the grinding stock are drawn into the nip by friction to crush one another in a product bed with the application of extremely high pressure.
The concept of the invention may be used in the original manufacture of rollers but is particularly well suited to provide a coating on the existent core of a roller that is not otherwise modified. The invention is applicable in two roller presses, but is particularly well suited in roller presses for interparticle crushing because of the high nip forces involved.
The concept of interparticle crushing involves a process wherein the bulk material is stressed between two practically nonyielding hard surfaces generally with a compression of at least 500 kg per square centimeter to result in energy sufficiently high not only to cause comminution but to cause a distinct agglomeration on briquetting of the particles whereafter the resulting agglomerates are disintegrated by further mechanical stressing in a separate device. Interparticle crushing, sometimes called product bed comminution is discussed in various prior art patents including U.S. Pat. Nos. 4,357,287 and 4,703,897 and European Patent 0 084 383. In the structures and processes of these patents, individual particles of the grinding stock are drawn into the nip by friction to crush one another upon the application of extremely high pressure in a product bed wherein the material fill is compressed between two roller surfaces. It will be evident that the roller surfaces are thereby exposed to extraordinarily high stress and wear.
It has been known to armor roller surfaces by welding layers of hard metallic materials onto the base roller cylinder. In such constructions, a one-part or a multi-part wear-resistant cladding of cast or rolled material is joined onto the base roller. The roller armor is welded on and has been constructed by welding annular layers lying side-by-side.
In order to improve the draw-in capability of the nip of pressing rollers, it must draw the product into the nip by friction and compress it. It is known to provide the cylindrical surface of the roller jacket with a profiling of beads arrange V-shaped and which are attached by additional manufacturing steps. Due to the creation of trough-shaped washouts in the region between the welding beads of the profiling welded on the roll, it had been shown that the. roller surfaces wears relatively quickly.
It is accordingly an object of the present invention to provide an improved roller for a high pressure roller press which has wear-resistant armoring on the surface which is constructed in a simplified fabrication method and has a high useful life despite profiling and particularly has a good product draw-in capability in the nip.
A further object of the invention is to provide an improved roller press wherein the rollers are capable of operating under particle crushing circumstances and wherein the rollers are armored and have good draw-in capabilities.